ABSTRACT
Earth retaining systems (ERS) are installed in order to facilitate excavations for the construction of underground transport infrastructure. The design and cost of an ERS can be highly dependent on the likely damage to nearby buildings caused by the excavation induced ground settlement. A safe ground settlement limit needs to be established in order to minimize damage to existing buildings.
At present there is no direct method to determine the limiting ground settlement for a safe level of building damage. In current design practice a preliminary level of building damage is determined using the estimated ground settlement which is based on the ERS design. An acceptable level of building damage is obtained through an iterative process of redesigning the ERS. This approach results in suboptimal design and cost. It is also time inefficient.
This paper presents a new concept of “Settlement Limit Curves”. These curves show the relationships between ground settlement, excavation depth and proximity to the retaining wall for the “Slight” building damage category. Reference to these curves will enable the design engineer to quickly and accurately determine the limiting ground settlement in order to restrict a building to “Slight” damage. The ERS may then be optimally designed using this information.
The curves may also be used as a preliminary damage assessment tool to quickly identify en masse, by proximity to the excavation, the buildings that exceed the “Slight” damage category. This function may be interpreted as a middle ground between the commonly used Stage I and II damage assessment procedures. This information may also be used as a guideline for planning the least damaging routes and positions for future underground infrastructure.
Keywords: Building damage, Foundations, Settlement, Limiting strain, Retaining systems.
